The present invention relates to carbon black and to processes for making carbon black. More particularly, the present invention relates to unique forms of carbon black and to several multi-stage carbon black forming processes.
The present invention relates to the production of carbon black such as furnace blacks having many important applications, such as fillers, pigments, and reinforcing agents, in rubbers and plastics. Generally, the furnace process for preparing these blacks entails the cracking and/or incomplete combustion of a hydrocarbon feedstock such as natural gas or catalytic cracker cycle stock in a closed conversion zone to produce carbon black. The carbon black entrained in the gases emanating from the conversion zone is then quenched and collected by any suitable means conventionally used in the art. It has, however, been extremely costly to produce carbon blacks having high surface area with increased structure.
U.S. Pat. No. 5,190,739 to MacKay et al. relates, in part, to a process for preparing carbon blacks having lower-than-normal structure at a given surface area and a lower-than-normal surface area at a given overall combustion level. The process can involve the use of a multi-stage furnace wherein a second source of hydrocarbons is added to the stream of hot first-stage gases. Certain embodiments of the '739 patent also relate to the use of potassium to make low structure carbon blacks. However, the amount of the auxiliary hydrocarbons used in the '739 patent are considerably lower amounts than in the first stage. Furthermore, the '739 patent can optionally use additional fuel and/or oxygen to achieve further combustion upon the introduction of the auxiliary hydrocarbons. In addition, there is no significant temperature zone difference between the zone where the first feedstock is introduced and the zone where the auxiliary feedstock is introduced in the '739 patent.
In U.S. Pat. No. 4,383,973 to Cheng, this patent relates to a process which involves two carbon black reactors in sequence where one of the reactors is for a high-structure carbon black and the second is for a low-structure carbon black. In the one figure of the '973 patent, the reactors are apparently connected together in sequence. However, in this process, additional air and fuel are introduced to the second feedstock and there is no significant temperature difference between the two feedstock introduction zones. Further, there is no partial quenching occurring prior to the complete quenching. The '973 patent further states that there is no quenching occurring between the first and second carbon black forming zones and further 10 ppm or more potassium can be introduced in the high structure zone. Furthermore, with the high combustion occurring in each feedstock introduction zone, there would not be any significant temperature zone difference between the first carbon black of high structure is formed and the zone where the low structure carbon black is formed.
In U.S. Pat. No. 4,976,945, a process for producing carbon black is described which uses various amounts of alkali metal, such as potassium, in a carbon black reactor to regulate structure. The '945 patent does state that an alkali metal compound and/or alkaline earth metal compound can be added in an amount of 500 to 50,000 ppm relative to the hydrocarbon starting material. The '945 patent does not relate to a multi-stage carbon black forming process and shows no partial quenching occurring prior to the complete quenching. The '945 patent further states that an alkali metal compound is particularly effective for the production of carbon black where the DBP absorption is at most 90 cc/100 g.
U.S. Pat. No. 4,822,588 to Gravely et al. relates to a carbon black reactor which has a first reaction zone and a second reaction zone that are serially connected. In this process, in the second stage, additional carbonaceous feedstock is introduced to form a second reaction mixture. In this process, the goal was to not substantially form carbon black in the first reaction zone. Also, the process didn't use an alkali metal or alkaline earth metal.
Accordingly, there is a need to provide a novel and improved process for preparing carbon blacks which exhibit improved or increased structure with increased surface area.
All of the patents and publications mentioned throughout are incorporated in their entirety by reference herein.